Undoped NiO Research Articles

One Pot Green Synthesis of Zr doped NiO Nanoparticles using Annona squamosa Seed Extract: Characterization and Biological Properties

Pure and Zr-doped NiO nanoparticles were successfully synthesized through green synthesis using extract of Annona squamosa seeds. The synthesized nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV-vis spectroscopy, field emission scanning electron microscopy (FESEM), EDAX (energy dispersive X-ray analysis) and elemental mapping analysis. The addition of zirconium dopant has been integrated into the single-phase NiO lattice structure as indicated by characterization findings. Furthermore, the antibacterial, antifungal and antioxidant properties of Zr-doped and undoped NiO NPs were thoroughly examined. As a result of the strong Zr-doped NiO NPs synergistic effect, the results showed that the Zr-doped NiO NPs have improved the biomedical properties when compared to the undoped NiO NPs. The optimized size and shape of the nanoparticles contributed significantly to their improved effectiveness against the microorganisms and oxidative stress.

Effects of Li concentration in the precursor solution on NiO thin films deposited using electrostatic spray deposition

Abstract Undoped and Li-added NiO thin films were deposited using electrostatic spray deposition (ESD) techniques. Initially, the NiO thin films displayed minimal contamination, predominantly C and H. The NiO thin films exhibited a flat surface morphology comprising grains of uniform size, approximately 20–30 nm in diameter, and reliable crystal growth, with a full width at half maximum of approximately 0.30 in X-ray diffraction analysis. Moreover, the NiO/ZnO diode demonstrated superior properties when a 5 at. % Li concentration solution was incorporated. The rectification ratio reached approximately 2.3 × 10³ at ± 1.0 V, with an ideality factor of 1.9. Additionally, the NiO/ZnO diodes exhibited remarkable photovoltaic properties even without detailed optimization. These findings underscore the potential of ESD in advancing semiconductor thin-film technology, thereby paving the way for more cost-effective and scalable production methods.

Electrochemical performance of cobalt-doped NiO thin films synthesized by spray pyrolysis

ABSTRACT In this work, various cobalt-doped NiO thin films have been synthesized via the spray pyrolysis. The cobalt-doped NiO thin films show a cubic phase with preferred orientation along the (111) plane. The scanning electron microscopy images of the cobalt-doped NiO thin films show interconnected flakes with small agglomerated particles. The optical bandgap decreases from 3.30 eV for the undoped NiO thin film to 2.90 eV for 20 mol% cobalt doping, with an increase in cobalt doping concentration in NiO. The electrochemical activities have been tested in 2M KOH electrolyte with cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. The highest specific capacitance observed for the 10 mol% cobalt-doped NiO thin film electrode is 760 Fg−1 at a scan rate of 5 mVs−1. The 10 mol% cobalt-doped NiO thin film electrode shows 92% retention in capacitance after 1000 cycles and a low charge transfer resistance of 10 Ωcm2.

Improved transparency and charge matching of electrochromic devices with Ce-doped NiO counter electrode

The quest for cost-effective and efficient electrochromic electrodes, featuring high color contrast and rapid response times, has sparked increasing interest in research of metal oxides for electrochromic applications. In this study, nickel oxide thin films with various cerium dopant concentrations are synthesized, with the optimized doping concentration identified as 1 at%. X-ray diffraction analysis confirmed that the dopant successfully reduces crystal size and alters the preferred orientation to (111). The 1 % Ce:NiO thin film exhibits enhanced electrochromic performance, with a transmittance modulation increase of 27.4 % at 633 nm, a 27.1 % rise in coloration efficiency and faster response time (tb=9.64 s and tc=6.76 s) compare to the undoped NiO. Importantly, the charge density of 1 % Ce:NiO thin film increases from 4.86 to 8.14 mC cm−2, representing a 67.5 % improvement, which becomes a better charge matching with WO3 in electrochromic devices. The incorporation of Ce into the NiO thin films not only leads to increased transmittance in the bleached state and optical modulation in the electrochromic devices but also contributes to a rise in the optical band gap of the NiO thin films and improved charge balance matching. These results underscore the positive impact of cerium doping on microstructure and electrochromic performance, indicating a promising future for electrochromic devices.

Green synthesis of undoped and Ag-doped NiO nanoparticles: Evaluation and their synergetic effect on antimicrobial, anticancer, and antioxidant activities

In this investigation, we successfully synthesized nickel oxide nanoparticles (NiO NPs) using a combustion method with Acacia nilotica gum as a biofuel, and systematically altered silver (Ag) concentrations within the NiO matrix. Post-calcination at 400 °C, various characterization techniques confirmed the formation, surface morphology, and crystalline characteristics of NiO NPs. The Ag-doped NiO NPs, particularly the NiAg4 sample, demonstrated remarkable antimicrobial efficacy, with superior activity against both fungal and bacterial pathogens. The NiAg4 sample also exhibited potent cytotoxicity against HT-29 human colon cancer cells, achieving an IC50 value of 1.5 mg/mL. Toxicological assessments revealed that both undoped and Ag-doped NiO NPs maintained biocompatibility with human red blood cells, indicating their potential for biomedical applications. Additionally, the NPs showed strong antioxidant activity and protein kinase inhibition, further supporting their therapeutic potential. These findings suggest that Ag-doped NiO NPs synthesized through a green protocol possess enhanced bioactivities, making them promising candidates for future in vivo studies and diverse biomedical applications.

Anion and Cation Co-Doping of NiO for Transparent Photovoltaics and Smart Window Applications

Materials engineering based on metal oxides for manipulating the solar spectrum and producing solar energy have been under intense investigation over the last years. In this work, we present NiO thin films double doped with niobium (Nb) and nitrogen (N) as cation and anion dopants (NiO:(Nb,N)) to be used as p-type layers in all oxide transparent solar cells. The films were grown by sputtering a composite Ni-Nb target on room-temperature substrates in plasma containing 50% Ar, 25% O2, and 25% N2gases. The existence of Nb and N dopants in the NiO structure was confirmed by the Energy Dispersive X-Ray and X-Ray Photoelectron Spectroscopy techniques. The nominally undoped NiO film, which was deposited by sputtering a Ni target and used as the reference film, was oxygen-rich, single-phase cubic NiO, having a visible transmittance of less than 20%. Upon double doping with Nb and N the visible transmittance of NiO:(Nb,N) film increased to 60%, which was further improved after thermal treatment to around 85%. The respective values of the direct band gap in the undoped and double-doped films were 3.28 eV and 3.73 eV just after deposition, and 3.67 eV and 3.76 eV after thermal treatment. The changes in the properties of the films such as structural disorder, direct and indirect energy band gaps, Urbach tail states, and resistivity were correlated with the incorporation of Nb and N in their structure. The thermally treated NiO:(Nb,N) film was used to form a diode with a spin-coated two-layer, mesoporous on top of a compact, TiO2 film. The NiO:(Nb,N)/TiO2heterojunction exhibited visible transparency of around 80%, showed rectifying characteristics and the diode’s parameters were deduced using the I-V method. The diode revealed photovoltaic behavior upon illumination with UV light exhibiting a short circuit current density of 0.2 mA/cm2 and open-circuit voltage of 500 mV. Improvements of the output characteristics of the NiO:(Nb,N)/TiO2 UV-photovoltaic by proper engineering of the individual layers and device processing procedures are addressed. Transparent NiO:(Nb,N) films can be potential candidates in all-oxide ultraviolet photovoltaics for tandem solar cells, smart windows, and other optoelectronic devices.

Cu-doped NiO thin film's structural, optical, and electrical properties and its negative absorption behaviour in the Infra-Red region

NiO undoped and Cu-doped thin films on FTO-coated glass (fluorine-doped tin oxide) are prepared by employing the sol-gel spin coating method. The Cu-doping effect was observed in all the characterized reports such as absorption, transmittance, field emission scanning electron microscope (FESEM), Grazing Incidence X-ray Diffraction (GIXRD), photoluminescence (PL), Raman spectra, current-voltage measurement (IV), and X-ray photoelectron spectroscopy (XPS). Enhancement in electrical conductivity due to Cu doping and IR illumination has been found. Band gap can also be tuned by varying doping concentrations. One new phenomenon called negative absorption (NA) has been found while investigating the optical properties in the infrared (IR) region for both undoped and Cu-doped NiO on the FTO substrate, which opens a new door for advanced research. The multifarious properties of NiO thin films offer various applications in many different fields.

Development of a new family of hole transport semiconductor oxides for fully transparent optoelectronic devices

Highly crystalline p-type NbxNi1-xO films have been prepared at various concentrations of Nb doping (x = 0–0.17) using a solution growth approach. The films exhibit cubic crystal structures with preferential orientation along the (200) plane. The Nb-doping of NiO films increases the lattice constant, lattice strain, and deformation energy density. The SEM images depict the increase in the grain size of NiO nanocrystals with increasing the Nb concentration. The EDS spectra inspect the stoichiometry of the prepared films. The AFM measurements revealed that the surface roughness increases from 0.4 nm to 2.1 nm with increasing Nb doping. The deposited films showed high optical transparency reaching 80 %. The optical bandgap energy decreases from 3.35 eV to 2.63 eV, and the Urbach tail energy decreases from 0.78 eV to 0.52 eV with the increase of Nb doping. The photoluminescence measurements reveal the suppression of the density of the Ni and O vacancies by 70 % due to the inclusion of Nb doping in the Ni sites. The electrical resistivity of the Nb-doped NiO films decreased by 200 times, the hole mobility increased by 12-fold, and the carrier density increased by 15-fold compared to un-doped NiO films. Owing to these outstanding properties, NbxNi1-xO films are a promising alternative to PEDOT: PSS for developing durable and efficient optoelectronic devices.

Influence of Cu-ion doping in NiO NPs and their structural, morphological, optical and magnetic behaviors for optoelectronic devices and magnetic applications

NiO and Cu-ion doped NiO nanoparticles with various concentrations (0.01–0.04 M) have been effectively synthesized in the current investigation using chemical precipitation method. The following techniques were used to characterized the materials’ structural, morphological, elemental analysis, functional group, optical and magnetic properties: XRD, TEM, HR-TEM, SAED, SEM, EDX, FTIR, UV, PL and VSM. According to this Scherrer formula, the average crystalline sizes of the materials of pure NiO and Cu-doped NiO were determined to be 16.37 nm, 15.21 nm, 14.88 nm, 18.35 nm, and 10.88 nm, respectively. The HR-TEM images revealed that the d-spacing values about 0.24 nm, which coincides with the (111) plane of cubic NiO for pure and copper doped NiO nanoparticles. The SEM micrographs of Cu-doped NiO nanomaterials shows tiny agglomerated particles, while that of pure NiO nanoparticles shows spherical structure. Pure NiO and Cu-doped NiO nanoparticles have band gap values of 2.32 eV, 2.29 eV, 2.24 eV, 2.22 eV, and 2.27 eV, respectively. The Cu-doped NiO nanoparticles (0.01–0.03 M) at various concentrations can significantly reduce the band gap without significantly altering the structure, making them a potential material for creating optoelectronic devices. Copper was incorporated into NiO nanoparticles, which had a significant impact on the magnetic properties and changed the material from weakly ferromagnetic to ferromagnetic. In comparison to undoped NiO nanoparticles, the saturation magnetization and coercivity values of the 0.01 M and 0.03 M of Cu-doped nanoparticles is much higher. This outcome demonstrates that such Cu-doped NiO nanoparticles have promising magnetic applications.

Magnetic properties of Fe-doped NiO nanoparticles

Undoped and Fe-doped NiO nanoparticles were successfully synthesized using a lyophilization method and systematically characterized through magnetization techniques over a wide temperature range, with varying intensity and frequency of the applied magnetic fields. The Ni1-xFexO nanoparticles can be described by a core-shell model, which reveals that Fe doping enhances exchange interactions in correlation with nanoparticle size reduction. The nanoparticles exhibit a superparamagnetic blocking transition, primarily attributed to their cores, at temperatures ranging from above room temperature to low temperatures, depending on the Fe-doping level and sample synthesis temperature. The nanoparticle shells also exhibit a transition at low temperatures, in this case to a cluster-glass-like state, caused by the dipolar magnetic interactions between the net magnetic moments of the clusters. Their freezing temperature shifts to higher temperatures as the Fe-doping level increases. The existence of an exchange bias interaction was observed, thus validating the core-shell model proposed.

Pre-solid-solution enhanced electrochemical performance of NiO-based thin films for Li-ion storage

Fabrication of an anode with high specific capacity is one of important strategies for improve the energy density of Li-ion batteries (LIBs). In present work, a ceramic target of Li-doped NiO solid solution (Ni0.96Li0.04O, denoted as NLO) was prepared for fabricating nanostructured thin films using magnetron sputtering. The electrochemical performance of prepared thin films for electrode application in LIBs was investigated. Compared with the undoped thin film, the predoped NLO thin films exhibited superior overall performance. The predoped NLO thin films provided an initial discharge specific capacity of 785 mAh g−1 (173 μAh cm−2) at 0.2C and maintained 666 mAh g−1 after 100 cycles, while the undoped NiO thin flm showed the ones of 534 and 319 mAh g−1, respectively. The predoped NLO thin films demonstrated outstanding rate performance with specific capacities ranging from 798 mAh g−1 at 0.2C to 384 mAh g−1 at 3.2C. Influence of pre-solid-solution doping on the superior electrochemical performance of NLO film was discussed taking account on predoping enhanced electronic conductivity of the thin films.

Preparation and characterisation of nickel oxide and nickel oxide codoped with magnesium and zinc

The present work focuses on the formulation and characterisation of undoped NiO and NiO codoped with Mg and Zn. The samples were characterized by x-ray diffractometer and ultraviolet-visible spectrophotometer. For the detection of elements present in the samples, energy dispersive x-ray analysis was employed. Two sets of codoped samples were prepared varying the amount of Mg and Zn. A set of codoped samples was prepared keeping the quantity of Mg at a fixed value and allowed the quantity of Zn to fluctuate. The second set of codoped samples was prepared keeping the extent of Zn at a fixed value and allowed the quantity of Mg to fluctuate. The bandwidth of undoped and codoped materials was computed raising Tauc plot. Crystallite size was computed following Scherrer formula.

Improvement of electrochromic performance of nickel oxide porous films by Sn doping

In order to alleviate some disadvantages such as slow switch speed, small light modulation, and poor cycle stability, which hinder the large-scale application of electrochromic (EC) materials, element doping has become one of important routes to improve their microstructure and performance. In this work, tin-doped nickel oxide (Sn-doped NiO) porous EC films were prepared, and the influence of Sn-doping amount on the microstructure and EC performance of NiO films was investigated by comparing with undoped NiO film. Based on the electrochemical tests and energy-band structure analyses, the influence mechanism of Sn doping was discussed. The results show that the Sn doping changed the surface energy of NiO nanoparticles, and then changed the microstructure, increased the diffusion rate of ions, and improved the light modulation of NiO films obviously. And the Sn doping reduced the interface barrier of FTO/NiO heterojunction, resulting into the rapid EC response. The Sn-doped NiO film with doping amount of 10.0 mol.% showed the best EC properties, including large light modulation (64.1% at 550 nm), short response time (0.4 s for bleaching time and 3.0 s for coloring time), high coloration efficiency (48.9 cm2 C−1), and long cycle life (30000 cycles), and its semiconductor type changed into n-type from the p-type of undoped NiO film.

Niobium-doped NiO as p-type nanostructured layer for transparent photovoltaics

Niobium-doped nickel oxide (NiO:Nb) thin films were investigated as p-type layer for all oxide transparent solar cells. The NiO:Nb films were grown by sputtering on room-temperature substrates in plasma containing 50% Ar and 50% O2 gases. The undoped NiO film was oxygen-rich, single-phase cubic NiO, exhibiting transmittance of less than 20%. Upon doping with Nb, the film remained p-type, the hole concentration increased from 4.3 × 1018 cm−3 to 1.2 × 1019 cm−3 but the optical properties remained almost the same with the undoped film. The changes in the properties of the films such as structural disorder, energy band-gap, Urbach states and resistivity were correlated with the incorporation of Nb in their structure. Improvement of the optical properties was achieved by thermal treatment at 300 °C. The visible transmittance increased to around 50% and the films showed a direct band-gap of 3.65–3.71 eV depending on the amount of Nb in the Ni-O structure. The optimum p-NiO:Nb film was used to form a diode with a spin-coated, mesoporous on top of a compact, TiO2 film. The p-NiO:Nb/n-TiO2 heterojunction became transparent after thermal treatment, showing rectifying characteristics. The diode showed photovoltaic behavior upon illumination with ultraviolet light exhibiting short-circuit current density 1.5 μA/cm2 and open-circuit voltage 200 mV. Transparent NiO:Nb films can be realized for all-oxide ultraviolet photovoltaics, tandem solar cells, solar-blind photodetectors and other optoelectronic devices.

Effect of Transition Metals Addition on the Nickel Oxide Catalyst toward Reduction Behaviour in Carbon Monoxide Atmosphere

The chemical reduction progression behaviour of transition metals (Mo, Zr, W, Ce, and Co) doped on NiO was studied using temperature programmed reduction (TPR) analysis. A wet impregnation method was applied to synthesise the doped NiO series catalysts. The reduction progress of the catalysts was attained by using a reductant gas at the concentration of 40% v/v CO/N2. X-ray diffraction (XRD) was employed to determine the composition of the reduced phases. Undoped NiO was reduced at 384℃ to obtain a cubic phase of NiO. It was observed that Ce/NiO exhibited the lowest reduction temperature of 370℃ among all catalysts. This phenomenon might be due to a higher surface area of Ce/NiO compared to undoped NiO, which facilitated a faster reduction reaction. The rest of the doped NiO series catalysts (Co/NiO, Mo/NiO, W/NiO and Zr/NiO) demonstrated a higher reduction temperature compared to undoped NiO. New peaks in the XRD pattern were observed only for the reduced catalysts of Mo/NiO and W/NiO, which were associated with monoclinic MoO2 and WO2.72 phases, respectively. The formation of new compounds or more stable nickel alloys led to a slower reduction reaction than undoped NiO. Therefore, Ce/NiO was the most efficient catalyst in promoting the formation of Ni under the CO atmosphere.

Enhanced electrochemical performance of facilely synthesized cobalt doped cubic NiO nanoflakes for supercapacitor application

Being inexpensive, nontoxic and environmental friendly, NiO has caught special attention as a promising electrode material for supercapacitors. We recently reported facile synthesis of porous NiO nanocrystallites for energy storage application. A sophisticated strategy to improve the electrochemical properties of NiO which is a p-type semiconductor is the incorporation of 3d metal ions into it. In this article, we present successful fabrication of highly porous cobalt doped NiO nanostructures through a facile, low cost, one step solution combustion method without a post calcination treatment and demonstrate the influence of cobalt content on structural properties and electrochemical behavior. The thus prepared Co doped NiO samples were systematically characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Field emission scanning electron microscopy, High resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller measurements, cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy. It was found that the phase structure of pristine NiO remains unaffected by the process of doping. But doping obviously influences the textural and morphological properties, more importantly, enhances the electrochemical properties of pristine NiO. A maximum specific capacity of 746 C/g (specific capacitance of 1244 F/g) was obtained for an optimum cobalt dopant ratio, which is superior to undoped NiO (295 C/g). Moreover, cobalt doped NiO nanostructures exhibited a good rate capability (71 % capacity retention from 1 to 15 A/g) and long term cycling stability (83.7 % after 5000 cycles at 100 mV/s). An asymmetric device fabricated using Co doped NiO electrode as the positive electrode and activated carbon as the negative electrode delivered an energy density of 32.7 Wh/kg at a power density of 261 W/kg.

The Effect of Au Nanoparticles on the Structural and Optical Properties of (NiO:WO3) Thin Films Prepared by PLD Technique

In the present investigation, (NiO:WO3 ) thin films were deposited at RT onto glass substrates using PLD technique employing focused Nd:YAG laser beam at 600 mJ with a frequency second radiation at 1064 nm (pulse width 9 ns) repetition frequency (6 Hz), for 400 laser pulses incident on the target surface .The structural, morphological and optical properties of the films doped with different concentration of Au content (0.03, 0.05, and 0.07) were examined with X-ray diffractometer(XRD), Atomic Force Microscope(AFM) , UV–Vis spectrophotometer . The results show that the films were amorphous with small peaks appearing when doped with AuNPs . The XRD peaks of the deposited NiO:WO3 were enhanced with increasing the Au content . The crystalline size of the deposited thin films was calculated using Debye Scherer formula and found to decrease from 6.6 nm for undoped NiO:WO3 to 3.4 nm for doped (NiO:WO3) with the increase of Au content from x=0 to x=0.07 at preferred orientation of (200). All the samples have a cubic structure. Also, the results showed that Au content of the films affects the surface morphology. From the results of AFM analysis, it was found that the roughness and average diameter change when adding Au to the structure, with the highest value occurring at Au ratio 0.03 equal to 7.58 and 81.02 nm, respectively. UV–Vis spectrophotometer was used to investigate the optical transmission. It was found that when Au content of films increased, the transmittance of films decreased.

Two-Dimensional Porous Structure of V-Doped NiO with Enhanced Electrochromic Properties.

In this work, a two-dimensional porous structure of a V-doped NiO film with excellent electrochromic properties on an ITO substrate was synthesized by a hydrothermal method. The influence of V5+ ions on the NiO film was explored by adjusting the amount of V doping, including refining the crystal grains, increasing the specific surface area of the film, and accelerating the diffusion rate of OH– in the film. Compared with the undoped NiO film, a 3 atom % V-doped NiO film comes out with superior electrochromic properties with large optical transmittance modulation (81.9% at 600 nm), fast response times (1.2 and 0.9 s), and excellent cycle stability (90.6%). This work creates innovation direction in the field of intelligent energy-saving window materials with high electrochromic properties.

Optimization of the performance of bulk NiO catalyst in the oxidative dehydrogenation of ethane by tuning the synthesis parameters

Highly stable and selective bulk NiO catalysts have been synthesized for the oxidative dehydrogenation (ODH) of ethane to ethylene. Interestingly, by optimizing synthesis parameters such as the amount of oxalic acid in the synthesis gel and the calcination temperature, undoped NiO catalysts have shown a consistent selectivity to ethylene of ca. 75%. The optimal catalyst requires the presence of a certain amount of oxalic acid in the synthesis gel and a final calcination at low temperatures (i.e. 350 °C). These catalysts have been deeply characterized by means of XRD, TPR, HRTEM, Raman and UV–vis diffuse reflectance spectroscopies, XPS and Electrochemical Impedance Spectroscopy measurements and tested in the ethane ODH. A novel electrochemical study has been undertaken, showing the p-character of all the NiO catalysts synthesized but differing in their capacitance values and density of cationic vacancies. The catalytic performance of NiO catalysts has been explained in terms of the different physicochemical properties (including changes in the number of vacancies) of the samples and the isolation of electrophilic oxygen species.

Cu doped NiO thin film photocathodes for enhanced PEC performance

The present report describes the fabrication of undoped NiO and Cu doped NiO based photocathodes synthesized by sol gel spin coating technique. Mott-Schottky, LSV and EIS measurements have been carried out to investigate the PEC properties of these photocathodes. 3% Cu doped NiO film exhibits the highest PEC performance among all photocathodes. The p-type semiconducting nature of all thin film samples has been confirmed from the M-S plots. Also, the values of carrier density have been tuned from 1.18 × 1020 to 1.36 × 1020 cm−3 for undoped NiO and 3% Cu doped NiO thin films. VB CB levels of the as-prepared photocathodes have been calculated from absorption spectra. 3Cu:NiO exhibits a significantly higher photocurrent density of −6.97 mA/cm2 at −1.5 V vs. Ag/AgCl in 0.1M NaOH solution under UV illumination. The superior PEC performance is due to efficient charge transport and reduced recombination rate of the photogenerated electron-hole pairs. These findings demonstrate the potential of Cu doped NiO photocathodes in water splitting applications.